CA1276170C - Benzylidenemalonic or vinylogous benzylidenemalonic acid polyesters, their preparation and their use for the uv stabilisation of thermoplastics - Google Patents

Abstract

BENZYLIDENEMALONIC OR VINYLOGOUS BENZYLIDENEMALONIC
ACID POLYESTERS, THEIR PREPARATION AND THEIR USE FOR
THE UV STABILIZATION OF THERMOPLASTICS
ABSTRACT OF DISCLOSURE
The present invention relates to new benzyli-dene-malonic or vinylogous benzylidenemalonic acid polyesters containing structural units of the formula (I)

Description

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New benzylidenemalonic or vinylogous benzylidenemalonic acid polyesters, their preparation and ~heir use for the UV stabilisation of thermoplastics .

The present invention rel~tes to ne~ benzyLidene-malon;c or vinylogous benzyLidenemalon;c acid poLyesters containing structural units of the formula tI) r ~ O ~
L-O~ a_O_I
I
e~ '~
I ~ I (I) a~
~herein R =i~ , C1-C4-alkyl or phenyl and t = 2ero, or R = H and t = 1, and X and r can be identical or different and are H, OH, methoxy, phenoxy, C1-C4-alkyl~ phenyl, Cl or ~r, and having moLecular we;ghts Mn (measured in a kno~n manner by means of vapour pressure osmosis or gel chromato-graphy) of about 970 to about 9~000, an OH number of 5-115 and a COOH number of O to 8.
Preferred polyesters are those of th.e formula tII) Le A 22 564-US
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tII) .;~3 wherein R1 is ~ethyl or ethyL, is methyl, ethyl or propyl and 'in~l is an integral number of 3 to 30, preferably ~O~to 25, which corresponds to an ~n of about 2~000 to 8,450.
The dihydroxy compounds which are suitabLe for the synthesis of the poLyesters according to the ;nvention are aLiphatic and~or cycloaLiphatic dihydroxy compounds and/or diphenoLs, and it is possible to empLoy, as a branching agent, alcohols having a functionality of more than 2, preferably aliphatic triols or aliphatic tetraols in amounts of 0 to 20 mole ~, preferably 5 to 15 mole %, relative to moles of dihydroxy compounds.
The new polyesters containing structural units of the for~ula ~I) can be prepared firstLy by a KnoevenageL
reaction from malonic acid polyesters and ~he aldehydes or ketones of the formula ~III) Le A 22 564 -US

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(~;)t ( I I I ) where;n R, t, X and Y have the meaning mentioned for formula tI).
S In th;s reaction it is poss;ble to have recourse to known general directions for the reaction, sueh as are listed, for example, in Organikum ("Organic Chemistry"~, VEB
Deutscher Verlag der Wissenschaften, ~erlin, 7th edition, in Chapter 7.2.4, pages 444-447.
The preparat;on of a malonic acid polyester which can be employed as the starting material in this reaction, namely malonic acid ethylene gLycol polyester, from di-ethjl malonate and ethylene glycol is described in Carothers, Aroin, J. Am. Chem. Soc. 51, 25~0 (~929).
Other starting polyesters of malonic acid can also be prepared analogously. Acîd catalysts, such as are generally kno~n for esterification and trans-esterifica-tion reactions, for example p-~oluenesulphonic acid, are preferably employed for the preparation of these poly-esters. It is preferable to employ, in this reaction, the lowest possible concentration of catalyst~ preferably O.b5 to 0.02X by weight~ relative to the total of the reactants, in order, on the one hand, to obtain a colour-less Product and, on the other hand, still to obtain a rapid reaction.
~ ranching can be induced in the starting poly-esters of malonic acid by concomitantly using~up to 20 mole X, preferably 5 to 15 mole X, relat~ve to moles of ' ~
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dihydroxy compounds, of alcohols hav;ng a funct;onality of Irore than 2, preferably aliphatic -triols or aliphatic tetrao1s.
In the Knoevenagel reaction the reactant rat;o of the C~ group in the startin~ polyester of malon;c acid o to the " group of ~ompound (III) is between 1:1 and 1:1.2.
C

The catalysts used are typical Knoevenagel catalysts, such as piper;dine/glacial acet;c ac;d or ammonium acetat~ or n-butylam;ne/glsc;al acet;c acid; examples of suitabLe solvents are aromat;c hydrocarbons, such as benzene, 1û toluene or xylenes. The use of an excess pressure or a vacuum ;s generalLy not necessary.
~ he present invention also relates, therefore, to a process for the preparat;on of polyesters containing structural un;ts of the for~ula (I),characterised ;n that malon;c ac;d polyesters having an Mn of about 50D to 5,000 are reacted with aldehydes or ketones of the formula tIII~
in the manner of a Knoevenagel reaction at temperatures between about 20C and about 150C, ;f appropr;ate ~;th the add;t;on of an inert solvent, ;n the presence of a Knoevenagel catalyst.
A further process for the preparat;on of poLy-esters conta;n;ng structural units of the formula tI) is the polycondensat;on of diesters of the for0ula tIa) O
R3--O ~ ~ O--R3 r C1~
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R, t~ X and r have the meaning mentioned for formula (I) and R3 ;s methyl or ethyL, ~ith al;phat;c and/or cycLoaliphat;c dihydroxy compounds and, if desired, alcohols having a functionality of more than 2, preferably aliphatic triols or aliphatic tetraols as branching agents in amounts up to 20 mole %, preferably 5 to 15 mole %, relative to moles of diyhdroxy compounds, at temperatures of 150 - 190C in the presence of acid 1~ or basic txans-esterification catalysts, such as, for example, tetrabutyl orthotitanate or potassium tert.-but~late, under nitrogen.
The present ;nvent;on also relates, therefore, toa process for the preparation of polyesters containing structural units of the formula ~I), characterised ;n that d;esters of the formula tla) are reacted ;n a known manner ~ith aliphat;c and/or cycloal;phat;c d;ols, and, ;f desired, ~ith up to 20 mole X, preferably 5 to 15 mole %, relative to moles of diols, of alcohols hav;ng a func-~ionality higher t~an 2, pr~ aliphatic triols or aliphatic tetraols,at temperatures of 150C to 190C in the presence of an ac;d or bas;c trans-esterif;cation catalyst, alcohol being removed by distillation.
The reaction time in the first preparation vari-ant is bet~een about 5 and 10 hours; in the second reac-tion var;ant the reaction time is about the same.
The isolation and purificat;on of the polyesters according to the invention is effected in a known manner, ~or example by washing ~ith ~ater and precipitation with 30 methanol.
The preparation process mentioned first is pre~
ferred~ because it results in products of higher molecular ueight ~hich are also characterised, in addit;on, by a markedly lo~er iodine colour number.
The polyesters accord;ng to the invention are suitable for use as UV stabilisers for thermoplastics, preferably for thermoplastic, aromatic polycarbonates, thermoplastic, aromatic polyesters and thermoPlastic poly-Le A 22 564-US

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C1-C4-alkyLme~hacrylates.
The present ;nven~io~ also relat~s~ th2refore, t~
the use of the polyesters accord;ng to the ;nvent;~n con-tain;ng structural un;ts ~f the formula (I) for the UV
stab;lisation of thermoplastics, preferable thermo-plastic, aromat;c polycarbona~es, thermopLast;c, aromat;c polyesters or thermoplastic poly-C1-C4-alkYLmethacryLates, preferably in amounts of D.1 to 1% by we;ght, relative to the ~eigh~ of thermoPlastic.
The ;ncorporat;on of the polymeric UV absorbers to be used in accordance with the ;nvent;on, conta;ning structural un;ts of the formula (I), ;nto the thermoplas-t~cs is effected by known techn;ques, for example by add;ng the polymeric UV absorber in und;Luted form to the polymer melt of the thermoplast;c or by apply;ng polymeric UV absorber to the sol;d plastic ~granules) by sp;nn;ng and subsequently extruding the mixture at the melt;ng temperature or by prepar;ng a combinat;on of plastics having a high content of UV absorbers (master batch) and subsequent~y mixing these concentrates ~ith further plastic.
The present invention also relates, therefore, to a process for the UV stabilisat;on of thermoplast;cs, preferable thermoplastic, aromatic polycarbonates, thermo-~5 Dlastic, aromatic polyesters or thermoplastic po~y-C1-C~-alkylmethacrylates, which is character;sed ;n that the thermoplast;cs are either homogenised ~;thout f~rther treatment, at temPeratures bet~een 250C and 320C, in a kno~n manner with the polymeric UY absorbers, according to the invention t containing structural units of the for-mula (I), in amounts suitable for UV citabilisation, pre ferably in amounts of 0.1 to 1 ~i by weight, relative `-`to the weig~t:of;~thermoplastic, or th~ polymeric UV- i absorbers are incorporated in the same manner at tempera-tures between 250C and 320C via the intermediate stageof a 5 to 10 per cent strength by weight ~oncentrate in the same thermoplastic.
The present invention also relates to UV stabi-Le A 22 564-VS

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lised thermoplastics~ preferable thermoplastic, aromatic polycarbonates, thermoplastic9 aromat;c poly-esters or thermoplastic poly-C1-C4~alkylmethacrylates having a content of polyesters, according to the inven-t;on~ conta;n;ng s~ruc~ural un;ts of the formula (I~,preferably having a content of û.1 to 1X ~y weight, rela-tive to the we;ght of thermoplast;c~
Polymer;c UV absorbers and their use for the UY
stab;lisat;on of plastics, ;n particular thermoplast;c polycarbonates, are kno~n (see DE-OS (German Published Specification) 2~231,531 and DE-OS (German Published Specification) 2,231,S32). However, the polymeric UV
absorbers described therein are C-C polymers con~ain;ng ester side ~roups, whereas the polyesters of the present invention have the es~er bonds in the main chain.
The polymeric UV absorbers according to DE-OS
(Berman Published Specification) 2,231,531 and according to DE-OS ~German Publ;shed Specification) 2,231,532 are resistant to sublimation and exhibit the advantage that 2n the extinction coefficients of the polymers, ~aking into account the UV absorbing constituent, are al~ays markedly higher than the extinction coefficients of the correspond-ing monomer mixtures tPages 3 and 4 of DE-OS ~German Pub-lished Specification3 2,231,531). In addition, they also stabilise, for example, polycarbonate moulding materials wh;ch have been p;gmented ~;th TiO2 ~ithout a reduction ;n molecular ~eight being observed and ~ithout a decline ~n the mechanical propert;es be;ng observed ~page 2 of DE-OS ~German Published SPec;f;cation) 2,231~532).
Ho~ever~ it is a disadvantage in the use of these polymeric UV absorbers that the protect;ve action against U~ is lower than tha~ of the corresponding commercially available monomeric UV absorbers, as is sho~n, for example, by the foLlo~ing comparison of compounds A and ~:

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0~ ,c~ ~0 3 Transmiss;on values after weathering (1,200 hours) and exposure (1,000 hours~ to Light of 420 nm.(~L420/CX]) S none g lamp ~20~X) WOM ~ 420(X) Compound lB)tO.5X by ~eight) 53.~X 72.5X
ComPound (A)(0.5% by ueight) 38.0X 67 D%
~hen the polymeric UV absorbers according to the 7nvention are used, ho~ever, th;s is not the case Examples of malon;c ac;d polyesters ~h;ch are suitable as starting material for the preparation of the UV absorbers to be employed in accordance with the inven-tion are the products obtained by trans-esterification, in a manner known from the literature, from diethyl malonate and aliphatic diols and/or cycloaliphatic diols andtor diphenols.
The follo~ng are examples of suitable aliphatic diols:: :
ethylene glycol, diethylene: glycol~ tetraethylen~e glycol, 1,2-propanediol, 1,3-propaned;ol, 1,2-butaned;ol, 1,3~
butanediol, 2j3-butanediol, 1,4-butanediol, 2,2-dimethyl-~3-Propanediol~ 1,5-pentaned;ol, 1~6-hexanediDl, 2,5-hexanediol, 2-methyl-2-p:ropy~ propanediol, 2,2-di-ethyl 1~3-propanediolO 2-ethyl-1~3-hexanediol~ 1,12-octa-decanediol and 1,:4-cyclohexanedimethanol.
Exomples of cycloa(;phatic diols which are su~t-able for the preparation of the m~alonic ac;d polyesters are 1,4-cyclohexanedlol or per~hydrobisphenol A, whiLe Le A 22 564-US

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: ' 7~3 examples of diphenol~ which 3re suitable for the prepara-t;on of the malon;c acid polyesters are 2,2-bis-(4-hydroxyphenyl)-prop~ne tbisphenol A), 1,1~bis-t4-hydroxy-phenyl)-cyclohexane, 2,2-bis-~3,5-dichloro 4~hydroxy-phenyl)-propane, 4,4'-d;hydroxybiphenyl and hydroquinone.
Examples of alcohols having a functionality h;gher than 2 are trimethylolpropane, glycerol or pentaerythritol.
Malonic acid polyesters ~hich are preferred for the preParat;on of the UV absorber~ accord;ng to ~he ;nvention are those of the formula (IV) ~ R1 l ~1 H ~ 2 2 ~ C~-CH2-C-~--CH2--C-CH OH

n ~herein ~1~ R2 and n have the meaning of formula (II)-Malonic acid polyesters wh;ch are very particu-lS larly preferred are those of the formula (IV) ~herein R1= R~ = CH3 and "n" is a number from 10 to 25.
The malonic acid polyesters to be employed as starting material for the preparation of the UV-absorbers in accordance with the invention should have average molecular weigh~s Mn ~number average) of about 500 to about 5,000 (measured in a known manner by means of vapour pressure osmosis or gel chromatography) they should have OH numbers of 5 to 20 and acid numbers of 2 to 9.
~xamples of suitable aldehydes or ketones of the formula (III) are 4-methoxybenzaldehyde, 4-hydroxybenz-aldehyde, 4-phenylbenzaldehyde, 4-hydroxy-2-methoxybenz-aldehyde, acetophenone, benzophenone and cinnamaldehyde; ~:
4-methoxybenzaldehyde and 4-phenylbenzaldehyde are par-ticularly preferred.
The follo~;ng are examples of suitable diesters : :
of the formula tIa): d;ethyl 4-methoxybenzyl;denemalonate~
dimethyl 4-methoxybenzylidenemalona~e, diethyl 4-hydroxy-Le A 22 564-US

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~ - 10 -ben~yLidenemalonate, dimethyl ~-hydroxybenzylidenemalonate, d;e~hyl 4-phenylbenzylidenemalonate and d~thyl 4-phenyl-b~n~yl;denemalonate~
l~ne aliphatic and cycloaliphd~ic diols and th~ alcohols having a functionality higher ~n 2 already mentioned for the preparation of start;ng polyest~rs of malon;c acid are also suitabLe as reactants for the preparation of the polymeric UV absor-bers according to the ;nvention from the diesters of the formula tIa) by the second preparation variant.
2,2-Dimethyl-1,3-propanediol, 2-meth 2 propyl-1,3-propanediol and 2,2-diethyl-1,3-propanediol are preferred dihydroxy compounds for the preparation of the ~olymeric UV absorbers or the starting polyesters of malonic acid; 2,2 dimethyl~1,3-propanediol is a par~icu~
larly preferred dihydroxy compound.
The benzylidenemalonic or v;nylogous benzylidene-malonic ac;d polyesters according to the invention con-ta;ning structural units of the formula (I) are viscous and resin-like produc~s or brittle and glass~like pro-ducts~ depending on their molecular weight. ~rittle andglass-like polyesters having softening poin~s of 30 to 70~C are preferred.
Examples of some of the benzylidenemalonic or vinylogous benzylidenemalonic ac;d polyesters according to the invention are p-methoxybenzylidenemalonic acid neopentyl glycol polyester (Mn approx~ 3,500), p methoxybenzylidenemalonic acid adipol polyester, P-methylbenzylidenemalonic acid neopentyLglycol polyester ~Mn approx, 3,500) and p-chlorobenzylidenemalonic acid neopentylglycol polyester.
In addition to the aromatic polyrarbonates, aromatic polyesters and thermoplastic poly-C1-C4-alkyl-methacrylates already mentioned, examples of thermoplastics which are suitable for UV stabilisation are further thermoplastic~ transparen~ plas~ics, such as cellulose esters, PVC or special grades of polystyrene.
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Thermoplastics ~hich can be s~abilised preferen-tially are thermoplastic, aromatic polycarbonates which can be obtained by reacting diphenols, especiaLly dihydroxydiarylalkanes, ~ith phosgene or dies~ers of carbonic acid, and, 35 ~ell as the unsubstituted dihydroxyd;arylalkanes, those having aryl radicals which carry methyl groups or halogen atoms ;n the o-posit;on and/or m-posit;on relat;ve to the hydroxyl group are also su;table. Branched polycarbonates are also suitable. Examples of chain terminators used are monophenols. Examples of branching 3gents are trisphenols or tetraphenols.
~ he polycarbonates to be stabilised have mean ~eight avera3e molecular weights M~ bet~een 10,000 and 100,000, preferably between 20,000 and 40,000, deter~ined by measurement of the relat;ve v;scosity ;n CH2Cl2 at 2SC and at a concentration of 0.5 9/100 ml.
Examples of su;table diphenols are hydroquinone, resorcinol, 4,4'-dihydroxybiphenyl, bis-(hydroxyphenyl)-alkanes, such as, for example, C1-C8-alkylenebisphenols or C2-C8-alkyl;denebisPhenols~ bis-thydroxyphenyl~-cycloalkanes, such as, for exampLe, cs-c15-crcloalkylene bisPhenols or C5-C15-cycloalkyl;denebisphenols, or bis-thydroxyphenyl) sulphides, ethers, ke~ones, sulphox-ides or sulphones. Also ~X'-bis-~hydroxyphenyl)-di;so-propylbenzene and the corresponding nuclear-alkylated or nuclear-halogena~ed compounds. Polycarbona~es based on 2,2-b;s-~4-hydroxyphenyl)-propane tbisphenol A), 2,2-bis-t4-hydroxy-3,5-dichlorophenyl)-propane (tetrachlorobis-phenol A), 2,2-bis-t4-hydroxy-3~5-di-bromophenyl)opropane ~tetrabromobiephenol A), 2,2-bis-(4-hydroxy-3,5-dimethyL-phenyl)-propane (tetra~nethylbisphenol A) and 1o1-b;s-(4-hydroxyphenyl)-cyclohexane tbisphenol Z) and also those based on trinuclear bisphenols, such as ~X'-bis-(4-hydroxyphenyl)-p-d;isopropylbenzene are preferred~
Further suitable diphenols and the preparation of the Le A 22 564-US

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pslycarbonates are described, ~or example, in U.S. Patents ~,02~,365, 3,062,781 and 3,879,347 Thermoplastics ~hich can be stabilised preferen-tially are also thermopLas~;c, aromat;c polyesters based on diphenols and terephthalic and isophthalic acid di-chlor;des (acid chlor;de rat;o 7:3 to 3:7, preferably 1 chain term;nators and, if appropr;ate, branch;ng agents.
The compounds mentioned above for the preparat;on of poly-carbonates are used as diphenols, cha;n term;nators and branching agents~
The aromat;c polyesters are prepared from the m;x-tures of acid chlorides, diphenols, chain terminators and~
if appropriate~ branching agents by the process of phase interface polycondensation. The relat;ve solut;on vis~
cosity of thè aromatic polyesters to be stabilised in accordance ~ith the invention should ~e between 1.18 and 2.0, preferably bet~een 1.2 and 1.5 tmeasured in a C~2C12 solution at 25C and at a concentration of 0.5 9/100 ml).
Plastics which can be stabilised preferentially are also thermoplastic poly-C1-C~-alkYlmethacrylates, that is to say polymers of C1-C4-alkyl methacrylates, for example methyl, ethyl, propyl or butyl methacrylate, ;i; preferably methyl or ethyl methacrylate. These are to be understood as meaning both ho~opolymers and copolymers of these methacrylic acid esters. In addi~ion~ up to a maxi-mum of 9.5X by ~ight of other ethylenically unsaturated, copolymerisable monomers, relat;ve in each case to the total weight of these unsaturated monomers and the meth-3~ acrylic acid esters, can be copolymerised, so that theC1-C~-alkylmethacrylate polymers to be stab;lised in accordance with the invention are composed of 90.5X by weight to 100X by we;ght of alkyl methacrylate units and of 9.5% by ~eight to OX by ~eight of oth~r ethylenically unsaturated monomer units.
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E~amples of other ethylen;cally unsaturated, co-polymer;sable monomers are (meth)acrylon;trile, (~ methyl)-styrene~ bromos~yrene, vinyl acetate, C1 C8-alkyl acrylates, aryl ~meth)acrylates, (meth)acrylic acid, ethylene, propylene, N-vinylpyrrol;done, vinylsulphonic acid (salts) or styrenesulphonic acid ~salts).
The polymethac~ylates WhiCll CaIl be preferably stabilised in accordance with the invention are substances soluble in certa;n organic solvents and thus possess a linear or branched structure.
The polyl[ethacrylates ~ ich can be preferably stabilised in accordance ~ith the invent;on can be prepared by kno~n polymer;sation processes, but preferably by free-radical or thermal polymerisation. Suitable polymerisation pro-cesses are processes carried out ;n emulsion, bulk~ sus-pension or dispersion, especially emulsion polymerisation, but preferably bulk polymerisation or solution polymerisa-tion. The molecular weights of the polymethacrylates can be varied ~ithin ~ide ranges by kno~n process-conditioned 2n measures, for example by the use of mercaptans as regula-tors. Usually the polyr[e~acrylates ~ ich can be preferably stabi-lised in accordance with the invention possess molecular ~eights (or Staudinger indices, or melt viscosities) of such a kind as to make it rational to carry out their ~S thermoplastic processing by injection moulding or extru-s;on.
Cellulose esters ~hich can be stabilised in accordance uith the invention are obtained in accordance ~ith customary processes by esterifying cellulose ~ith aliphatic monocarboxylic anhydrides, preferably acetic and butyric anhydrides or acetic and propionic anhydrides.
The h~drolysis to be carr;ed out in the crude soLution is controlled by means of a slight excess of ~ater so that a lo~ hydroxyl content (4 to 25) is obtained~ The oxidative bleaching of the cellulose esters isolated from the solu-tion must be carr;ed out ;n such a ~ay that oxidis;ng Le A 22 564-uS

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agent can no longer be detecte~ in the end product; if necessary, an after-treatment with reducing agents must be carried out.
The OH number is determined by ester;fying ~he free hydroxyl groups of ~he cellulose ester ~ith acet;c anhydr;de in pyrid;ne; the excess anhydride is reacted ~ith ~ater and back-t;trated ~D;rect;ons: C.J. MahnO
L.B7 Genung and R.F. ~;lliams, Analysis of Cellulose Der;vat;ves, Industrial and Engineering Chem;stry, Volume lG 14, No. 12, ~35-940 (1942)~.
The Yiscosity of the cellulose esters should be 0.3 to 0.5 po;se, measured ;n the form of a 20% strength solution ;n acetone. Cellulose esters which can be used preferent~ally have an acet;c ac;d content of 17 to 23X
15 by ue;ght and a butyr;c acid content of 45 to 50X by ~e;ght in the case of the acetobutyrate, and a propionic ac;d content of 61 - 6~X by weight and an ace~ic acid content of 2 to 7X by we;ght in the case of the aceto~
propionate. The OH numbers are usually between 4 and 25.
~he mean we;ght averages of the molecular ~eights Mw are bet~een 10,000 and 1,000,000, preferably betueen 100,000 and 500,000.
PVC grades ~h;ch can be stab;lised ;n accordance with the invention are emuls;on PVCO suspension PVC and bulk PVC. The Fikentscher K-values, measured in cyclo-hexanone ~lX stren~th solution at 23C)~ are bet~een 50 and 80.
Spec;al transparent grades of polystyrene ~hich can be stabil;sed ;n accordance ~;th the ;nvent;on are homopolymers of styrene or copolymers of styrene ~hich preferably conta;n acrylon;trile and/or butadiene and~or malon;c acid esters, and are obtained at an Mw of 10,000 -~00,000 from the monomers or m;xture of monomers by, for example, suspension polymerisation in the presence of catalysts. tM~ ;s measured in DMF at c = 5 ~/litre and 2nC). (~or literature on this see: Beilste;ns Hand-Le A 22_564-l;~S

buch der Organischen Chemie ("Beilstein's Handbook of Organic Chem;stry"), fourth edition, third supplemen~, Volume 5, pages 1163-1169, Springer Verlag 1964, and H~
Ohl;nger, Polystyrol, 1. Teil, Herstellungsverfahren und S Eigenschaften der Produkte ("Polystyrene, Part 1, Prepara-t;ve Processes and Properties of the Products"~, Spr;nger Verlag 1955).
The process;ng of the thermoplastics containing the incorporated poLymeric UV absorbers accord;ng to the invention can be carried out by the kno~n methods of extrusion or cast;ns to give a very wide var;ety of shaped articles, in particular sheeting and panels, including, for example, double-webbed panels as specified in ~P-OS
tEuropean Published Specification) 0 054,856 The extrusion can be carried out ~ith or ~ithout the application of a vacuum in customary extruders at temperatures o f 250C to 320C, in a manner de~end-ing on the nature of the plastic to be extruded. Virtu-ally no evaporation of the UV absorber according to the invention takes place in the course of this~
A parttcularly advantageous application of the polymeric UV absorbers according to the invention is use in thermoplastic polycarbonate films in concentrations of 1% by ueight to 15X by ~eight, preferably 3X by weight to 7X by ~eight~ relative to the ueight of the film, these films being used in a thickness of 10 to 100 lum, prefer-ably 20 to 50 ~um, for covering shaped articles made of thermoplastics, for example of the thermoplastic poly-carbonates~ aromatic polyesters or thermoplastic poly-methylmethacrylates mentioned above. Coverings of thistype and their application are known (see, for example, DE-OS tGerman Published Specification) 10694,Z74 and DE-OS
tGerman Publ;shed Spec;fication) 2,832,676). Particular advantages are afforded for the co~extrusion of multi-layer`systems in vacuo, above all in comparison ~ith theuse of monomeric benzylidenemaLonic ac;d esters according Le A 22 564-US

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to 6erm~n Patent SPecification 1,087,902 or DE-OS (German Published Specification) 2~310~135~ ~hich can lead, above alL in the case of vacuùm extrusionO because of their evaporat;on, to problems relating to the equipment and the quality of the extruded shaped articLes.
The present invention aLso reLates, therefore, to fiLms of thicknesses from 1û to 100 ~m, preferably 20 to 50 ~um, composed of thermopLastic, aromatic polycarbonates hav;ng a content of 1X by weigh~ to 15X by weight, prefer-ably 3X by ~eight to 7X by weigh~, of the benzylidene-malon;c or vinylogous benzyLidenemalonic acid poLyesters according to the invent;on contain;ng structural units of the formula ~ relative to the ~eight of the film.
The ;nvent;on also relates to the use of such polycarbonate f;lms for cover;ng shaped articles composed of thermoplast;cs, particularly using the co-extrusion process.
Examples of shaped articles which are particularly su;table for cover;ng are hollo~ cavity panels or double-2û ~ebbed panels accord;ng to ~P-OS ~European Published S~ec;ficat;on) 0,û54,856.
It is kno~n that monomer;c compounds of the benzyl;denemalonic ester type, for example diethyl 4~
phenylben~yl;denemalonate, have a Lower light stabilising action than UV absorbers of the ben triazole type, for examPle`2-t2-hydroxy-3-tert. butyl-5-sec.-bu~ylphenyl)-benztriazole. Monomer;c benzylidenemalon;c esters are therefore usually employed in concentrat;ons approx. 5ûX
greater than benztr;azoles. The polymeric UV absorbers 3û accord;ng to the ;nvention not only exhibit a better stab;lis;ng act;on than the corresponding monomeric l;ght stabil;sers, but a light stabilis;ng act;on is also ach;eved wh;ch is even better than that of benztr;azoles ~hich are currently commercially ~vailable, for example 2-~2-hydroxy-3-tert~-butyl-5-sec.-butylphenyl~-benztri-azole ~see Example C.1).
Le ~ 22 564-US

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~ 17 -It is also known that monomeric compounds of the benzylidenemalonic ester type, for example d;ethyL 4-phenylbenzylidenemaLonate, produce a certa;n falling-o~f in the mechanical properties, for example the notched impact strength, in plasti~s. Surprisingly, at comparable concentrations the UV absorbers accord;ng to the ;nvention exhib;t an ;mproved!notched impact strength (see Example In add;tion, the polymeric UV absorbers according to the invention are also more stable against extraction by ra~nwater than monomeric, commercially available li~ht stab;l;sers, particularly than hydroxyphenylbenztriazoles To the thermoplastics, stabilised according to instant invention, can be added other stabilizers, anti-15 oxydation agents, mould release agents and flame retardingadditives which are usual and known for each of the thermo-plastics to be modified; examples are phenols, metal-desactivating agen~s, sterically hindered amines etc..
The thermoplastics, stabilised according to 20 instant invention, are used preferably in areas which are exposed to high light radiation, for example for con-structing greenhouses, for electrical lamps, for furniture and for casing of free:air installations.
Examples A.1. Preparation of a malonic a id polyester from 2,2-dimethyl-1~3-propanediol and diethyl malonate.
3,200 9 of diethyl malonate and 2,080 9 of 2,2-dimethyl-1,3-propanediol (neopentylglycol) are heated at 140-150C in a stirred kettle, so that ethanol distils off. ~hen half the calculated quantity has distilled off, the mix~ure is heated at 170 180C for 1 hour so that reflux takes pl3ce. Ethanol is then distilled off again and a uaterpumP vacuum is applied~ 3,189 ~ (~3X~ of h;ghly v;scous malonic acid polyester are obtained~ Mn 2,800 ~determined by vapour pressure osmosis), OH number 24-25 and acid number 2-3.
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B.1. Preparation of a benzyl;denemalonic ~cid poLyester from the above malonic acid polyester ~A~
A solut;on of 903 9 of malonic acid neopentylgly-col polyester~ 714 g of anisaldehyde~ 4701 9 of ~ alanine and 47.~ 9 of glacial acetic acid in 2,600 ml of toLuene is bo;led under a ~ater separator for 12 hours. After filtrat;on and removal of the solvent by distilLation, 2 litres of methanol are added and the mixture is stirred under reflux for 1 hour at 100C. The phases are separated and the polyester is dried for 4 hours at 150C under a waterpumP vacuum. The polyester prepared in this ~ay has a molecular weight Mn of approx~ 4,500 (determined by gel chromatography); OH number 11-13 and acid number <1;
so~tening point 56C.
B.2. Preparation of a benzylidenemalonic acid poLyester from a monomeric benzylidenemalonic acid ester by the polycondensation process.
~ mixture of 5506 9 of diethyl p methoxybenzyl;-d~nemalonate (B), 32 g of tr~methyl-1,6-hexanediol an~ 0.2 g of K ~ert.-butylate is heated at 160-19DC 50 that ethanol distils off. ~hen the calculated amount of ethanol has been removed, the mixture is allo~ed to cool. The orange-coloured residue solidifies uhen cold to give a tough mass. The softening point of the mass îs about 55C. 5 C 1. Preparat;on of a stabilised polycàrbonate shaped 2rticle Bisphenol A polycarbonate in granular form (~ rel = 1.310, measured in 0.5 9/100 ml of tH2-Cl (s;c) at 25C) is mixed ~ith 0.3X by ~eight of the 4-methoxy~ 0 ben2ylidenemalonic acid neopentyl polyester from Example (~.1) by so-called application by spinning. The granules are then extruded at ~00C in a twin-shaft extruder to give a r;bbo~ ~hich i5 chopped up into granules again.
Hollo~ cavity panels are produced from these granules by the customary extrusion process.
Le A 22 564-US

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Test;ng the UV stabil;sing acgion Hollo~ cavity panels 10 mm thick, produced in the manner descr;bed above, ~ere subjected to ~eathering in a Q.U.V. acceLerated ~eathering dev;ce tXmax = 313 ~l1) for 3,000 nours. For comparison, 10 mm hollow cavity panels made of ~he same polycarbonate and containing 0.3X
of 2-(2-hydroxy-3-ter~.-butyl-5-sec.-butylphenyl)~benz-triazole, ~hich had also been produced in the manner des-cribed above, were tested at the same time. The light transmission factor at 450 nm was determined. The results of the tests are listed in Table 1.
Table 1 Artificial weathering of hollo~ cavity panels in a Q.U.V. device 10 mm hollo~ cavity Light transm;ss;on at 450 nm panels made of poly-~arbonate and contain;ng a) In;t;ally 1,000 hours 3,000 hours 0.3X of 4-methoxy_ -~0 benzyl;dene neopentyl polyester B1.2X 77.7X 74.6X
b) 0.3X of 2-~2-hydroxy-3-tert.-butyl-5-sec.-butylphenyl)-b~triazole ~1.3X 76.7X 72.2X
C.2. Production of a stabilised polycarbonate shaped article B;sphenol A polycarbonate in granular form ~hrel = 1.310, measured in 9.5 9/100 ml of CH2Cl2 a~ 25C) is mixed w;th 0.3~ by ~e;ght, 2% by we;ght and SX by weight of the 4-methoxybenzylidenemalonic açid neopentyl Le A 22 564-US

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polyester from Example (~.1) by so-called application by sp;nning. The granules are then extruded ;n a t~in-shaft extruder at 300C to give a ribbon ~hich is chopped up again into granules. Small standard bars are prepared from these granules by the customary injection moulding process. The no~ched impact strength of these small standard bars is determined as specified in DIN 53,453.
~he results are l;sted ;n Table 2.
Compound (~), ~ly d;ethyl ~-methoxybenzyL;dene-malonate ;s ;ncorporated analogously as a comparison com-pound; the results are also ;ncluded ;n Table 2.
Table 2 Hotched ;mpact strength of polyrarbonate contain;ng as additive d;ethyl 4-methoxybenzyl;denemalonate tB) and polymer;c UV absorber accord;ng to Example (B.1), in mJ/mm2, Concentrat;on 0.3 2 5X by ~eight ______________ _____________________________ UV absorber 30.1 16 5.0 (B) UV absorber ~ 40 21 10.0 (B.1) Le A 22 S64-US
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Claims (22)

1. A benzylidenemalonic or vinylogous benzylindenemalonic acid polyester containing structural units of the general formula (I) wherein R denoted hydrogen, C1-C4-alkyl or phenyl and X and Y
are identical or different and denote hydrogen, hydroxyl, methoxy, phenoxy, C1-C4-alkyl, phenyl, chlorine or bromine, characterized in having a number average molecular weight of 970 to 9,000, an OH number of 5 to 115 and a COOH number of 0 to 8.

2. A polyester according to Claim 1 of the general formula (II) wherein R1 denotes methyl or ethyl, R2 denotes methyl or propyl and n is an integral number of 3 to 30, inclusive.
Mo-2629-Ca -21-

3. A polyester according to Claim 2 in which n is a number of 10 to 25, inclusive.

4. A process for the production of a polyester having a number average molecular weight of 970 to 9,000 an OH number of 5 to 115 and a COOH number of 0 to 8 comprising reacting a malonic acid polyester having a number average molecular weight of 500 to 5,000 in the manner of a Knoevenagel reaction at a temperature between 20° and 150°C in the presence of a Knoevenagel catalyst, with an aldehyde or ketone of the general formula (III) wherein R denotes hydrogen, C1-C4-alkyl or phenyl and X and Y
are identical or different and denote hydrogen, hydroxyl, methoxy, phenoxy, C1-C4-alkyl, phenyl, chlorine or bromine.

5. A process according to Claim 4, in which the catalyst is piperidine/glacial acetic acid, or ammonium acetate or n-butylamine/glacial acetic acid.

6. A process according to Claim 4, in which the solvent is an aromatic hydrocarbon.

7. A process according to Claim 4, in which the malonic acid polyester is a compound of the general formula (IV) in which R1 and R2 both denote methyl and Mo-2629-Ca -22-n is a number from 10 to 25, inclusive.

8. A process according to Claim 4, in which the aldehyde of formula (III) is 4-methoxybenzaldehyde or 4-phenylbenzaldehyde.

9. A process according to Claim 4, in which the reaction is carried out using 5 to 15 mole %, relative to moles of diol, of the alcohol having a functionality higher than 2.

10. A process according to Claim 4, in which the alcohol having a functionality higher than 2 is an aliphatic triol or an aliphatic tetraol.

11. A process according to Claim 4, in which the diol is 2,2-dimethyl-1,3-propanediol.

12. A process for the UV stabilization of thermoplastic materials in which the thermoplastic material is directly homogenized without further treatment at a temperature between 250°C and 320°C with a UV-stabilizing amount of a polyester according to Claim 1.

13. A process for the UV stabilization of thermoplastic materials, in which a polyester according to Claim 1 is incorporated in the thermoplastics material by homogenization at a temperature between 250°
and 320°C via the intermediate stage of the formation of a 5 to 10% strength by weight concentrate of the polyester in the thermoplastics material prior to mixture of this concentrate with further thermoplastics material.

14. A process according to Claim 12 or 13 in which the polyester is finally present in an amount of 0.1 to 1% by weight, relative to the weight of the thermoplastics material.

15. UV stabilized thermoplastics material containing a polyester according to Claim 12 or 13.

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16. A film 10 to 100 µm thick composed of a thermoplastic, aromatic polycarbonate containing 1% by weight to 15% by weight, relative to the weight of the film, of a polyester according to Claim 1.

17. A method of producing a covered shaped article comprising, applying to a shaped article made of a thermoplastic material, a covering of a polycarbonate film as defined in Claim 16.

18. A process for the production of a polyester which is characterized in having a number average molecular weight of 970 to 9,000, an OH number of 5 to 115 and a COOH number of 0 to 8, comprising reacting a diester of the general formula (V) wherein R denotes hydrogen, C1-C4-alkyl or phenyl and X and Y
are identical or different and denote hydrogen, hydroxyl, methoxy, phenoxy, C1-C4-alkyl, phenyl, chlorine or bromine, and R3 is methyl or ethyl with an aliphatic and/or cycloaliphatic diol and 0 to 20 mole %, relative to the moles of said diol, of an alcohol having a functionality higher than 2 at a temperature of 150 to 190°C in the presence of an acid or a basic transesterification catalyst, with removal of alcohol by distillation.

19. A polyester prepared by the process of Claim 4.

20. A method for stabilizing a thermoplastic against UV radiation which comprises incorporating a UV
stabilizing amount of the polyester defined in Claim 1 into said thermoplastic.

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21. A polyester prepared by the process of Claim 18.

22. A method for stabilizing a thermoplastic against UV radiation comprising incorporating a UV
stabilizing amount of the polyester of Claim 21 into said thermoplastic.

Mo-2629-Ca -25-